In a steam boiler gas plant, natural gas is combusted to heat up hot water in a boiler to generate steam at sufficient temperature and pressure to spin a turbine and generator to produce electricity. This is the simplest method of producing steam and the likely the type of system that would be considered at Pickering if the engineering study indicates connecting a natural gas boiler to the existing steam turbines and generators is feasible.
Should the engineering study conclude that installing a standalone natural gas power plant would be the better option, a natural gas turbine based power plant would be the least expensive option. Turbine efficiencies are generally around 42-48%, which are much higher than for gas boiler type plants utilizing standard steam turbines, which are only around 30-35% efficient in converting thermal energy to electricity. There would certainly be an opportunity to recover some of the waste heat for use in green houses and water production.
A combined-cycle gas turbine power plant consists of one or more gas turbine generators equipped with heat recovery steam generators to capture heat from the gas turbine exhaust. Steam produced in the heat recovery steam generators powers a steam turbine generator to produce additional electric power. Use of the otherwise wasted heat in the turbine exhaust gas results in high thermal efficiency compared to other combustion based technologies. If it is ultimately determined from an engineering study that an entirely new gas plant would be more feasible and economical than connecting the Pickering plant’s power blocks to a gas boiler, then a combined-cycle gas turbine power plant of this type would be recommended for Repurposing Pickering. The third graphic at right depicts a 510 MW GE combined cycle natural gas plant being installed in France by GE for EDF. It is schedule to come online in mid-2016 and achieve 61% efficiency. Compared to standard steam turbine efficiency at around 33%, this plant promises to be nearly 85% more efficient and will be the most efficient gas plant in the world. To generate 2000 MW of electricity at Pickering would require 4 of these plants. More information on this particular plant example is available at http://www.zdnet.com/article/ges-flex-technology-natural-gas-plant-heading-to-france/.
According to Environment Canada, approximately 5% (31 million megawatt hours) of all electricity generated in Canada is attributed to the combustion of natural gas, accounting for about 9,500 megawatts of capacity. Boilers account for less than 20% of this capacity whereas gas turbines account for slightly more than 75%. The remaining capacity results from the operation of internal combustion engines. Gas turbine plants fuelled by natural gas are considered one of the cleanest fossil fuel-fired options available for the electric power generation. Since natural gas contains no ash and practically no sulphur or metals, emissions of these substances are virtually zero.
According to the US EPA, the average emissions rates in the United States from natural gas-fired generation are: 1135 lbs/MWh (Mega Watt hours) of carbon dioxide, 0.1 lbs/MWh of sulfur dioxide, and 1.7 lbs/MWh of nitrogen oxides. Compared to the average air emissions from coal-fired generation, natural gas produces half as much carbon dioxide, less than a third as much nitrogen oxides, and one percent as much sulphur oxides at the power plant.
NG Plant with Steam Boiler
NG Plant with Gas Turbine
NG Combined Cycle Plant with Gas Turbine and Steam Turbine